Deposition method using a uniform electric field

ABSTRACT

A deposition method includes placing a substrate on a susceptor inside a chamber, the susceptor including a center pin passing through the susceptor for lifting the substrate, energizing an electrode to applying a uniform electric field to the substrate, electrically connecting a ground member extending along and attached to an entire axial length of the center pin to a ground voltage source, and forming a film on the substrate by chemical vapor deposition.

The present application is a Continuation of U.S. patent applicationSer. No. 10/144,806 filed May 15, 2002, now U.S. Pat. No. 7,081,165issued Jul. 25, 2006, which claims the benefit of Korean PatentApplication No. P2001-27128 filed in Korea on May 18, 2001, both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chemical vapor deposition apparatus,and more particularly to a chemical vapor deposition apparatus forcreating a uniform electric field.

2. Description of the Related Art

In general, a liquid crystal display (LCD) controls a lighttransmittance of liquid crystal cells that are arranged in a matrixarray on a liquid crystal display panel. Accordingly, the liquid crystalcells receive data signals, thereby displaying an image (picture). TheLCD includes electrodes for supplying an electric field to a liquidcrystal layer, a thin film transistor (TFT) for switching the datasignals provided to the liquid crystal cells, a lower substrate havingsignal wiring for supplying the data signals to the liquid crystal cellsand signal wiring for supplying control signals of the TFT, an uppersubstrate having a color filter, a spacer formed between the uppersubstrate and the lower substrate for providing a predetermined cellgap, and liquid crystal molecules disposed within a space providedbetween the upper substrate and the lower substrate.

During fabrication of the liquid crystal display device, a channelportion in an active layer of the TFT and a protective layer protectingthe TFT are formed during plasma enhanced chemical vapor deposition(PECVD) processing. During PECVD processing, a gas is injected into avacuum chamber. Then, at a specific pressure and substrate temperature,the injected gas decomposes into a plasma by use of a radio frequency(RF) voltage, thereby depositing materials onto a surface of thesubstrate. A quality of the deposited material is dependent upon thedeposition conditions, such as the vacuum, the RF voltage, the RFvoltage frequency, substrate temperature, reaction gas, and reactionpressure, for example. In addition, the deposited materials includesinsulating films, semiconductor films, gate insulating films, protectivefilms, and etch stopper films. The semiconductor films include amorphoussilicon (a-Si:H) that form an active layer, and doped amorphous silicon(n+a-Si:H) that form a contact protective layer.

FIG. 1 is a cross sectional view of a plasma enhanced chemical vapordeposition (PECVD) apparatus according to a related art. In FIG. 1, thePECVD apparatus includes a gas jet 9 for releasing a gas to be depositedonto a substrate 7, and a chamber 1. The chamber 1 includes a susceptor5 for applying heat via a heating coil to the substrate 7, an arrow pin10 for securing the substrate 7, and a center pin 12 for separating thesusceptor 5 from the substrate 7.

During processing, the substrate 7 is placed upon the susceptor 5 withinthe chamber 1, and the susceptor 5 applies heat to the substrate 7 andfunctions as a lower electrode for generating a plasma. A temperature ofthe susceptor 5 averages about 370° C. In addition, the susceptor 5includes various pins formed to penetrate the susceptor 5.

The arrow pin 10 secures the substrate 7 within the chamber 1, and thecenter pin 12 rises by a pin plate 16 to prevent any drooping of thesubstrate 7. In addition, the center pin and pin plate 16 preventsformation of any scratches between a robot arm 14 and the substrate 7during loading and unloading of the substrate 7. The pin plate 16includes a center pin-supporting portion 18 having the center pin 12passing through it.

FIGS. 2A to 2D show a process for loading a substrate into a chamberaccording to the related art.

In FIG. 2A, the substrate 7 is loaded into the chamber 1 by the robotarm 14, and the substrate 7, the susceptor 5, and the center pin 12 arenot mutually contacting each other.

In FIG. 2B, the pin plate 16 rises to mount the center pin-supportingportion 18 in center pin mount portions 20 and 21 equipped on a rearsurface of the susceptor 5, and each of corner pins 22 and 23 and thecenter pin 12 rise by a power driver (not shown) to lift the substrate7.

In FIG. 2C, the robot arm 14 is separated from the substrate 7 by thepower driver (not shown).

In FIG. 2D, the susceptor 5 rises by a susceptor-lifting portion 24 tomake the susceptor 5 lift the substrate 7 and the center pin 12. Then,the susceptor 5 raises the substrate 7 close to the arrow pin 10.Accordingly, the substrate 7 is safely placed into a depositionposition.

FIG. 3 is a cross sectional view representing an inside of a chamberaccording to the related art. In FIG. 3, the chamber 1 includes thesubstrate 7 safely placed upon the susceptor 5, and an upper electrode30 that faces the substrate 7 with a predetermined gap therebetween. Thecenter pin 12 raises the substrate 7 upon loading, and the susceptor 5rises. Accordingly, the substrate 7 sustains a predetermined gap fromthe upper electrode 30, and the center pin 12 lowers into a center pinhole 19 formed on the susceptor 5. The center pin 12 is made of ceramicmaterial that has a low coefficient of thermal expansion.

FIG. 4 is a cross sectional view of a center pin according to therelated art as shown in FIG. 3. In FIG. 4, an insulating film Al₂O₃ isformed upon a head portion 3 of the center pin 12, thereby preventingelectrical arcing during plasma processing. Accordingly, the center pin12 is not ground to the susceptor 5. However, the heating coil (notshown) formed inside the susceptor 5 is ground with an external groundvoltage source GND.

In FIG. 3, a radio frequency (RF) voltage source 32 is connected to theupper electrode 30. Accordingly, an electric field is generated betweenthe upper electrode 30 and the substrate 7, whereby an insulating filmor a semiconductor film is deposited upon a surface of the substrate 7.When depositing the insulating film or the semiconductor film on thesubstrate 7, the electric field emanating from the upper electrode 30 isbowed in a region of the center pin 12. Accordingly, an electric fielddensity in a region of the center pin 12 is relatively low, thereby athickness of the deposition film in the region of the center pin 12 willbe thinner than surrounding regions.

FIG. 5 shows a defect resulting from the center pin according to therelated art. In FIG. 5, a thickness of the deposition film in an area Aof the substrate 7, which corresponds to a region of the center pin 12(in FIG. 3), is different from a thickness of the deposition film inother regions.

FIG. 6 is a spectrum photograph showing the defect on a substrateillustrated in FIG. 5 according to the related art. In FIG. 6, thethickness of the deposition film in the area A of the substrate 7, whichcorresponds to the region of the center pin 12 (in FIG. 3), isrelatively thinner than the thickness of the deposition film in theother regions.

FIG. 7 is a graph showing thickness distribution of a deposition film ofthe substrate 7 (in FIG. 5) taken along I-I′ of FIG. 6. In FIG. 7, thegraphical distribution of deposition thickness of the deposition film onthe substrate indicates that a defect is generated in a regioncorresponding to the center pin 12 (in FIG. 3). Accordingly, the defectdegrades image quality of the liquid crystal display device.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a chemical vapordeposition apparatus and method of using the same that substantiallyobviates one or more of the problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a chemical vapordeposition apparatus and method of using the same to generate a uniformelectric field, thereby forming a deposition film having a uniformthickness.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a chemicalvapor deposition method includes placing a substrate on a susceptorinside a chamber, the susceptor including a center pin passing throughthe susceptor for lifting the substrate, energizing an electrode toapplying a uniform electric field to the substrate, electricallyconnecting a ground member extending along and attached to an entireaxial length of the center pin to a ground voltage source, and forming afilm on the substrate by chemical vapor deposition.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a cross sectional view of a chemical vapor depositionapparatus according to a related art;

FIGS. 2A to 2D show a process for loading a substrate into a chamberaccording to the related art;

FIG. 3 is a cross sectional view of an inside of a chamber according tothe related art;

FIG. 4 is a cross sectional view of a center pin according to therelated art, as shown in FIG. 3;

FIG. 5 shows a defect resulting from the center pin according to therelated art;

FIG. 6 is a spectrum photograph showing the defect on a substrateillustrated in FIG. 5 according to the related art;

FIG. 7 is a graph showing thickness distribution of a deposition film ofthe substrate taken along I-I′ of FIG. 6;

FIG. 8 is a cross sectional view showing an exemplary chamber accordingto the present invention;

FIG. 9 is a cross sectional view of an exemplary center pin according tothe present invention; and

FIG. 10 is a cross sectional view of another exemplary center pinaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 8 is a cross sectional view showing an exemplary chamber accordingto the present invention. In FIG. 8, a chemical vapor depositionapparatus may include a chamber 50 for performing a deposition processon a substrate 37. The chamber 50 may include a susceptor 45 contactingthe substrate 37, a center pin 42 for lifting the substrate 37, and anupper electrode 40 facing the substrate 37 and having a predeterminedgap therebetween for generating an electric field.

The substrate 37 may be placed onto the susceptor 45 within the chamber50. A heating coil (not shown) may be formed within the susceptor 45 tosupply heat to the substrate 37. The susceptor 45 may also function as alower electrode for generating a plasma discharge. During the depositionprocess, a temperature within the susceptor 45 may average about 370° C.The susceptor 45 may include various pins (not shown) that pass throughthe susceptor 45 for chemical vapor deposition.

The center pin 42 may be elevated by means of a pin plate 36 to preventany drooping of the substrate 37. The pin plate 36 prevents any of thesubstrate 37 by a robot arm (not shown) during loading and unloading ofthe substrate 37. In addition, the pin plate 36 functions to raise thecenter pin 42 via a power driver (not shown).

FIG. 9 is a cross sectional view of an exemplary center pin according tothe present invention. In FIG. 9, the center pin 42 may include a headportion 53, a head supporter 54, and a grounding terminal 52. The headportion 53 may include a conductive segment 53 a formed of aluminum(Al), for example, and an insulating segment 53 b such as aluminum oxide(Al₂O₃), for example. The insulating segment 53 b may prevent electricalarcing between the substrate 37 and the susceptor 45 when the electricalfield is applied between the susceptor 45 and the upper electrode 40 (inFIG. 8).

The head supporter 54 may be formed of a ceramic material, for example,having a low coefficient of thermal expansion. A ground line 56 may beformed at one side of the head supporter 54. The ground line 56 may beformed of an electrically conductive metal such as aluminum (Al), forexample, inserted into a groove formed at one side of the head supporter54 and electrically interconnected to the conductive segment 53 a of thehead portion 53.

The ground terminal 52 may be electrically connected to the conductivesegment 53 a of the head portion 53 via the ground line 56, therebygrounding the center pin 42 to an external ground voltage source GND.The grounding the center pin 42 may be accomplished by electricallyconnecting a lower part of the center pin 42 to the ground terminal 52after removing a portion of the ground terminal 52 that has been coatedwith the insulating segment 43 b. Then, the ground terminal 52 may beconnected to a metal line that extends from a lower part of thesusceptor 45, thereby electrically grounding the center pin 42 to theexternal ground voltage source GND.

In FIG. 8, the upper electrode 40 may receive a voltage from a radiofrequency voltage source 38 to form a deposition film on the substrate37. Accordingly, since the center pin 42 is grounded to the groundvoltage source GND via the ground line 56, a uniform electric field isgenerated between the susceptor 45 and the upper electrode 40. Thisuniform electric field results in a deposition film have a uniformthickness across a surface of the substrate 37, and prevents formationof any defects within a region of the center pin 42.

FIG. 10 is a cross sectional view of another exemplary center pinaccording to the present invention. In FIG. 10, the center pin 42 mayinclude a head portion 53, a head supporter 54, and a grounding terminal52. The head portion 53 may include a conductive segment 53 a formed ofaluminum (Al), for example, and an insulating segment 53 b such asaluminum oxide (Al₂O₃). The insulating segment 53 b may preventelectrical arcing between the substrate 37 and the susceptor 45 when theelectrical field is applied between the susceptor 45 and the upperelectrode 40 (in FIG. 8).

The head supporter 54 may be formed of a ceramic material, for example,having a low coefficient of thermal expansion. A ground line 56 may beformed passing through a center part of the head supporter 54, and maybe formed of an electrically conductive metal, for example, and mayelectrically interconnect the conductive segment 53 a of the headportion 53 to an external ground voltage source GND via the groundingterminal 52.

The ground terminal 52 may be electrically connected to the conductivesegment 53 a of the head portion 53 via the ground line 56, therebygrounding the center pin 42 to an external ground voltage source GND.The grounding the center pin 42 may be accomplished by electricallyconnecting a lower part of the center pin 42 to the ground terminal 52after removing a portion of the ground terminal 52 that has been coatedwith the insulating segment 43 b. Then, the ground terminal 52 may beconnected to a metal line that extends from a lower part of thesusceptor 45, thereby electrically grounding the center pin 42 to theexternal ground voltage source GND.

In FIG. 8, the upper electrode 40 may receive a voltage from a radiofrequency voltage source 38 to form a deposition film on the substrate37. Accordingly, since the center pin 42 is grounded to the groundvoltage source GND via the ground line 56, a uniform electric field isgenerated between the susceptor 45 and the upper electrode 40. Thisuniform electric field results in a deposition film have a uniformthickness across a surface of the substrate 37, and prevents formationof any defects within a region of the center pin 42.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the chemical vapordeposition apparatus of the present invention without departing from thespirit or scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

1. A deposition method, comprising the steps of: placing a substrate ona susceptor inside a chamber, the susceptor including a center pinpassing through the susceptor for lifting the substrate up and down;applying a first voltage source to the susceptor; electricallyconnecting a connection member extending along and attached to an entireaxial length of the center pin to the first voltage source; applying asecond voltage source to a counter electrode to generate a uniformelectric field between the counter electrode and the substrate; andforming a film on the substrate by chemical vapor deposition.
 2. Themethod according to claim 1, wherein placing of the substrate includespositioning the substrate in contact with a head portion of the centerpin, the head portion being supported by a head supporter.
 3. The methodaccording to claim 2, wherein the connection member is formed betweenthe head portion and the head supporter.
 4. The method according toclaim 2, wherein the connection member passes through a center portionof the head supporter.
 5. The method according to claim 2, wherein theconnection member is formed along one side of the head supporter.
 6. Themethod according to claim 2, wherein the head portion includes aluminum.7. The method according to claim 2, wherein the head supporter includesa ceramic material.
 8. The method according to claim 2, wherein the headportion is formed with a conductive material, and the head supporter isformed with a material having a low coefficient of thermal expansion. 9.The method according to claim 2, wherein the head portion is coated withan insulating material.
 10. The method according to claim 1, wherein theconnection member includes an electrically conductive metal.
 11. Themethod according to claim 1, further comprising heating the substrate.12. The method according to claim 11, wherein heating the substrateincludes energizing a heating coil within the susceptor.